This project has continued studies of intracardiac flow dynamics with digital acquisition and analysis of color Doppler ultrasound imaging techniques for quantifying pathophysiologic hemodynamic abnormalities. Using hydrodynamic principles (jet flux theory, momentum continuity preservation, centerline acceleration, proximal flow convergence and turbulent/viscous interactions), temporal and spatial quantitation of flow events are possible. In the clinical management of valvular regurgitation, accurate evaluation of the severity of regurgitation is of major importance. Doppler echocardiographic techniques have enhanced the non invasive assessment of valvular regurgitation. However, there have been, heretofore, no studies related to the clinical applicability of these techniques using strictly quantified reference standards for validation. The current year's efforts have extended previous years' studies in an animal model of chronic aortic regurgitation: 1) A new Doppler flow calculation method which semiautomatically integrates digital spatial and temporal color flow velocity data has been validated for quantitation of regurgitant flow. 2) Three-dimensional reconstruction of regurgitant proximal flow convergence documented its asymmetric hemielliptical geometry which permitted calculation of peak regurgitant flow rates. 3) An excellent agreement was present between electromagnetically derived flow rates and those obtained from three-dimensional direct integration of flow convergence arc lengths to provide flow convergence surface area. 4) Three-dimensional reconstruction of left ventricular volumes permitted calculation of ejection volumes, regurgitant volumes and regurgitant fractions. Non invasive Dopler methods, thus validated in vivo, provide reliable information about the severity of cardiac valvular regurgitation to aid patient clinical management.